JP7025201B2 - Rubber composition for tires and pneumatic tires using them - Google Patents

Description

The present invention relates to a rubber composition for a tire and a pneumatic tire using the same.

Conventionally, in a rubber composition used for a tire, it is required to have a high-level balance between grip performance (wet grip performance) on a wet road surface and rolling resistance performance that contributes to low fuel consumption. However, since these are contradictory characteristics, it is not easy to improve them at the same time.

In response to such a problem, Patent Document 1 describes from a (meth) acrylate-based polymer having a predetermined structural unit and having no reactive silyl group with respect to 100 parts by mass of a rubber component made of a diene-based rubber. A rubber composition containing 1 to 100 parts by mass of fine particles having a glass transition point of −70 to 0 ° C. and an average particle size of 10 nm or more and less than 100 nm is disclosed.

Japanese Unexamined Patent Publication No. 2017-110069

However, such particles may contain impurities such as emulsifiers depending on the synthesis method, and the presence of metal elements contained in the emulsifiers or the like causes heat generation in the composition, resulting in low fuel consumption. There was room for further improvement in sexuality.

In view of the above points, it is an object of the present invention to provide a rubber composition for a tire capable of improving the wet grip performance and the fuel efficiency of the tire.

The rubber composition for a tire according to the present invention has an alkyl (meth) acrylate unit represented by the formula (1) as a constituent unit with respect to 100 parts by mass of a rubber component made of a diene rubber, and has a sodium concentration and potassium. It is assumed that the polymer particles having a total concentration of 2000 ppm or less are contained in an amount of 1 to 100 parts by mass, and sodium or potassium in the polymer particles is present as a fatty acid salt or a persulfate .

In the formula, R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, and R ² in the same molecule is. It may be the same or different.

The glass transition temperature of the polymer particles can be set to −70 to 0 ° C.

The pneumatic tire according to the present invention shall be manufactured by using the rubber composition for a tire.

According to the rubber composition for a tire of the present invention, the wet grip performance and the fuel efficiency of the tire can be improved.

Hereinafter, matters related to the practice of the present invention will be described in detail.

The rubber composition for a tire according to the present embodiment is formed by blending a rubber component made of a diene-based rubber with polymer particles made of a specific (meth) acrylate-based polymer.

Examples of the diene rubber as a rubber component include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), and chloroprene rubber (CR). Examples thereof include butyl rubber (IIR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, etc., and these are used alone or in combination of two or more. be able to. Among these, at least one selected from the group consisting of NR, BR and SBR is preferable.

Specific examples of each diene rubber listed above include at least one selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, an alkoxy group, an alkoxysilyl group, and an epoxy group at the molecular end or in the molecular chain. By introducing the functional group of the seed, the modified diene rubber modified by the functional group is also included. As the modified diene rubber, modified SBR and / or modified BR are preferable. In one embodiment, the diene-based rubber may be the modified diene-based rubber alone or a blend of the modified diene-based rubber and the unmodified diene-based rubber. In one embodiment, 30 parts by mass or more of the modified SBR may be contained in 100 parts by mass of the diene rubber, 50 to 90 parts by mass of the modified SBR and 50 to 50 parts by mass of the unmodified diene rubber (for example, BR and / or NR). It may contain 10 parts by mass.

The polymer particles are composed of a (meth) acrylate-based polymer having an alkyl (meth) acrylate unit represented by the following general formula (1) as a constituent unit (also referred to as a repeating unit). Those having a total amount of sodium concentration and potassium concentration in the polymer particles of 2000 ppm or less are used. The total amount of the sodium concentration and the potassium concentration is preferably as low as possible, more preferably 1800 ppm or less, but may be 100 ppm or more from the viewpoint of cost. Here, the sodium concentration and the potassium concentration are values measured by inductively coupled plasma emission spectrometry (ICP-OES). In addition, sodium and potassium include those existing as fatty acid salts and persulfates in the polymer particles.

In the formula, R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, and R ² in the same molecule is. It may be the same or different. The alkyl group of R ² may be linear or branched. ^R2 is preferably an alkyl group having 6 to 16 carbon atoms, and more preferably an alkyl group having 8 to 15 carbon atoms.

The (meth) acrylate-based polymer is obtained by polymerizing a monomer containing one kind or two or more kinds of alkyl (meth) acrylates. Here, (meth) acrylate means one or both of acrylate and methacrylate. Further, (meth) acrylic acid means one or both of acrylic acid and methacrylic acid.

Examples of the alkyl (meth) acrylate include n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-nonyl acrylate, and n-acrylic acid. Decyl, n-undecyl acrylate, n-dodecyl acrylate, n-tridecyl acrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, n-heptyl methacrylate, n-octyl methacrylate, N-alkyl (meth) acrylates such as n-nonyl methacrylate, n-decyl methacrylate, n-undecyl methacrylate, and n-dodecyl methacrylate; isobutyl acrylate, isopentyl acrylate, isohexyl acrylate, isoheptyl acrylate. , Isooctyl acrylate, Isononyl acrylate, Isodecyl acrylate, Isoundecyl acrylate, Isododecyl acrylate, Isotridecyl acrylate, Isotetradecyl acrylate, Isobutyl methacrylate, Isopentyl methacrylate, Isohexyl methacrylate, Isoheptyl methacrylate, Isooctyl methacrylate , Isoalkyl (meth) acrylates such as isononyl methacrylate, isodecyl methacrylate, isoundesyl methacrylate, isododecyl methacrylate, isotridecyl methacrylate, and isotetradecyl methacrylate; 2-methylbutyl acrylate, 2-ethylpentyl acrylate, acrylic. Examples thereof include 2-methylhexyl acrylate, 2-ethylhexyl acrylate, 2-ethylheptyl acrylate, 2-methylpentyl methacrylate, 2-methylhexyl methacrylate, 2-ethylhexyl methacrylate, 2-ethylheptyl methacrylate and the like. .. These can be used alone or in combination of two or more.

Here, isoalkyl means an alkyl group having a methyl side chain at the second carbon atom from the end of the alkyl chain. For example, isodecyl refers to an alkyl group having 10 carbon atoms having a methyl side chain at the second carbon atom from the chain end, and is a concept including not only an 8-methylnonyl group but also a 2,4,6-trimethylheptyl group. Is.

As one embodiment, the (meth) acrylate-based polymer is preferably a polymer having a structural unit represented by the following general formula (2) as a structural unit represented by the formula (1).

In formula (2), R ³ is a hydrogen atom or a methyl group (preferably a methyl group), and R ³ in the same molecule may be the same or different. Z is an alkylene group having 1 to 15 carbon atoms, and Z in the same molecule may be the same or different. Z may be linear or branched.

The structural unit of the formula (2) is a case where R ² in the formula (1) is represented by the following general formula (2A).

Z in the formula (2A) is the same as Z in the formula (2).

Examples of the (meth) acrylate that produces such a structural unit include the above-mentioned isoalkyl (meth) acrylate. When a (meth) acrylate having such an isoalkyl group (preferably methacrylate) is used, the effect of this embodiment can be easily enhanced. Z in the formulas (2) and (2A) is preferably an alkylene group having 5 to 12 carbon atoms, and more preferably an alkylene group having 6 to 10 carbon atoms. Particularly preferably, it is an alkylene group having 7 carbon atoms, and as an example, the (meth) acrylate-based polymer is preferably a polymer of a monomer containing isodecyl methacrylate.

In another embodiment, the (meth) acrylate-based polymer may be a polymer having a structural unit represented by the following general formula (3) as the structural unit represented by the formula (1), or may also be used. A polymer having a structural unit represented by the formula (2) and a structural unit represented by the formula (3) may be used. In the latter case, the addition form of both structural units may be random addition or block addition, and is preferably random addition.

In formula (3), R ⁴ is a hydrogen atom or a methyl group (preferably a methyl group), and R ⁴ in the same molecule may be the same or different. Q ¹ is an alkylene group having 1 to 6 carbon atoms (preferably 1 to 3), may be linear or branched (preferably linear), and Q ¹ in the same molecule may be the same or different. ^Q2 is a methyl group or an ethyl group (preferably an ethyl group), and ^Q2 in the same molecule may be the same or different.

The structural unit of the formula (3) is a case where R ² in the formula (1) is represented by the following general formula (3A).

In formula (3A), ^Q1 and ^Q2 are the same as ^Q1 and ^Q2 in formula (3), respectively.

When the (meth) acrylate-based polymer is a copolymer of such a structural unit of the formula (2) and a structural unit of the formula (3), excellent wet grip performance and rolling resistance performance can be easily obtained. In addition, it is easy to suppress the decrease in hardness of the rubber composition at room temperature, and it is easy to obtain excellent steering stability. In addition, it is easy to suppress an increase in the elastic modulus of the rubber composition at a low temperature, and it is easy to obtain excellent grip performance.

Here, specific examples of the (meth) acrylate that produces the structural unit of the formula (2) in the copolymer include the above-mentioned isoalkyl (meth) acrylate, and particularly preferably isodecyl methacrylate. Further, as a specific example of the (meth) acrylate that produces the structural unit of the formula (3), among the alkyl (meth) acrylates listed above, those excluding n-alkyl (meth) acrylate and isoalkyl (meth) acrylate. , And particularly preferably 2-ethylhexyl methacrylate.

In the case of such a copolymer, the ratio (copolymerization ratio) of the structural unit of the formula (2) to the structural unit of the formula (3) is not particularly limited. For example, the molar ratio of the structural unit of the formula (2) / the structural unit of the formula (3) may be 30/70 to 90/10 or 40/60 to 85/15.

The (meth) acrylate-based polymer constituting the polymer particles according to the present embodiment may be a homopolymer of the above-mentioned alkyl (meth) acrylate, but according to a more preferable embodiment, a large amount of alkyl (meth) acrylate is used. It is a polymer having a crosslinked structure that is crosslinked by the presence of a functional vinyl monomer. That is, in a preferred embodiment, the (meth) acrylate-based polymer contains a structural unit derived from the polyfunctional vinyl monomer together with the structural unit represented by the formula (1), and the structural unit derived from the polyfunctional vinyl monomer. It has a cross-linking structure having a cross-linking point.

Examples of the polyfunctional vinyl monomer include compounds having at least two vinyl groups that can be polymerized by free radical polymerization, and examples thereof include diols or triols (eg, ethylene glycol, propylene glycol, 1,4-butanediol, 1,4). Di (meth) acrylate or tri (meth) acrylate of 6-hexanediol, trimerol propane, etc.; alkylene di (meth) acrylamide such as methylenebis-acrylamide; at least 2 such as diisopropenylbenzene, divinylbenzene, trivinylbenzene, etc. Examples thereof include vinyl aromatic compounds having a vinyl group, and these can be used alone or in combination of two or more.

The (meth) acrylate-based polymer is not particularly limited, but the molar ratio of the constituent units of the formula (1) to all the constituent units (all repeating units) constituting the (meth) acrylate-based polymer is 50 mol%. The above is preferable, more preferably 80 mol% or more, still more preferably 90 mol% or more. The upper limit of the molar ratio of the structural unit of the formula (1) is not particularly limited, but for example, when the above-mentioned polyfunctional vinyl monomer is added, it may be 99.5 mol% or less, or 99 mol% or less. The molar ratio of the constituent units based on the polyfunctional vinyl monomer may be 0.5 to 20 mol%, 1 to 10 mol%, or 1 to 5 mol%.

In one embodiment, when the (meth) acrylate-based polymer is a polymer having the structural unit of the formula (2), the molar ratio of the structural unit of the formula (2) to all the structural units of the polymer is 25 mol%. The above is preferable, and more preferably 35 mol% or more, 50 mol% or more, or 80 mol% or more may be used. The upper limit of the molar ratio is not particularly limited, but for example, when a polyfunctional vinyl monomer is added at the above molar ratio, it may be 99.5 mol% or less, or 99 mol% or less.

In one embodiment, when the (meth) acrylate-based polymer is a polymer having the structural unit of the formula (3), the molar ratio of the structural unit of the formula (3) to all the structural units of the polymer is 25 mol%. The above is preferable, and more preferably 35 mol% or more, 50 mol% or more, or 80 mol% or more may be used. The upper limit of the molar ratio is not particularly limited, but for example, when a polyfunctional vinyl monomer is added at the above molar ratio, it may be 99.5 mol% or less, or 99 mol% or less.

Further, in another embodiment, when the (meth) acrylate-based polymer is a copolymer of the structural unit of the formula (2) and the structural unit of the formula (3), the formula (for all the structural units of the copolymer) The molar ratio of the constituent units of 2) may be 25 to 90 mol%, the molar ratio of the constituent units of the formula (3) may be 5 to 60 mol%, and the molar ratio of the constituent units of the formula (2) may be 35 to 85 mol%. In%, the molar ratio of the constituent units of the formula (3) may be 8 to 55 mol%. Further, the total molar ratio of the structural unit of the formula (2) and the structural unit of the formula (3) may be 80 mol% or more, 90 mol% or more, and the upper limit thereof is, for example, a polyfunctional vinyl monomer as described above. When added in a molar ratio, it may be 99.5 mol% or less, or 99 mol% or less.

In the present embodiment, the (meth) acrylate-based polymer preferably does not have a reactive silyl group. That is, in the present embodiment, since the polymer particles are not blended as a reinforcing filler in place of silica, the reactive silyl group is formed at the molecular end or the molecular chain of the (meth) acrylate-based polymer constituting the polymer particles. It is preferable that the particles do not have. This makes it easy to obtain excellent wet grip performance and rolling resistance performance. In addition, it is easy to suppress the decrease in hardness of the rubber composition at room temperature, and it is easy to obtain excellent steering stability. In addition, it is easy to suppress an increase in the elastic modulus of the rubber composition at a low temperature, and it is easy to obtain excellent grip performance. Here, the reactive silyl group is a functional group represented by the formula: ≡Si—X (in the formula, X is a hydroxyl group or a hydrolyzable group), and 1 to 3 hydroxyl groups or It is a group having a structure in which a hydrolyzable monovalent group is bonded to a tetravalent silicon atom. Examples of X include a hydroxyl group, an alkoxy group, and a halogen atom.

In the present embodiment, the glass transition temperature (Tg) of the polymer particles made of the (meth) acrylate-based polymer is not particularly limited, but is preferably −70 to 0 ° C., preferably −50 to −10 ° C. More preferably, it is more preferably −40 to −20 ° C. The glass transition temperature can be set by the monomer composition or the like constituting the (meth) acrylate-based polymer. When the glass transition temperature is 0 ° C. or lower, it is easy to more effectively suppress the deterioration of low temperature performance. Further, when the glass transition temperature is −70 ° C. or higher, it is easy to enhance the effect of improving the wet grip performance. Here, the glass transition temperature is measured at a heating rate of 20 ° C./min (measurement temperature range: −150 ° C. to 150 ° C.) by a differential scanning calorimetry (DSC) method in accordance with JIS K7121. The value.

In the present embodiment, the average particle size of the polymer particles is not particularly limited, but is preferably 10 nm to 100 nm, more preferably 20 to 90 nm, and further preferably 30 to 80 nm. When the (meth) acrylate-based polymer containing the specific structural unit is added to the diene-based rubber as such fine particles, excellent wet grip performance and rolling resistance performance can be easily obtained. In addition, it is easy to suppress the decrease in hardness of the rubber composition at room temperature, and it is easy to obtain excellent steering stability. In addition, it is easy to suppress an increase in the elastic modulus of the rubber composition at a low temperature, and it is easy to obtain excellent grip performance. Here, in the present specification, the "average particle size" is a value obtained by the cumulant method. Specifically, it is the particle size (50% diameter: D50) at an integrated value of 50% in the particle size distribution measured by the dynamic light scattering method (DLS), and is measured by the photon correlation method (JIS Z8826 compliant) (based on JIS Z8826). The angle between the incident light and the detector is 90 °), and it is a value obtained by the cumulant method from the obtained autocorrelation function.

The method for producing the polymer particles is not particularly limited, and for example, it can be synthesized by using a known emulsion polymerization. A preferred example is as follows. That is, the (meth) acrylate is dispersed in an aqueous medium such as water in which an emulsifier is dissolved together with a polyfunctional vinyl monomer as a cross-linking agent, and a water-soluble radical polymerization initiator (for example, potassium persulfate) is added to the obtained emulsion. By adding (peroxide) of As other methods for producing polymer particles, known polymerization methods such as suspension polymerization, dispersion polymerization, precipitation polymerization, mini-emulsion polymerization, soap-free emulsion polymerization (emulsion-free emulsion polymerization) and microemulsion polymerization can be used.

The polymer particles obtained by the above production method, particularly the polymer particles produced by using a polymerization method such as emulsion polymerization or suspension polymerization using an emulsifier, are organic having an sp value of 8 to 11 as required. After the redispersion treatment with a solvent, a coagulant may be added and the recoagulation treatment may be carried out to prepare the polymer particles so that the total amount of the sodium concentration and the potassium concentration is 2000 ppm or less.

The organic solvent having an sp value of 8 to 11 is not particularly limited, and examples thereof include tetrahydrofuran (THF), acetone, toluene, methyl ethyl ketone (MEK), xylene, methyl isopropyl ketone, methyl propyl ketone, ethyl benzene, and pyridine. Be done. The sp value (solubility parameter) referred to in the present specification is, for example, "Practical Polymer for Engineers" by Junji Mukai and Noriyuki Kaneshiro (Kodansha, published on October 1, 1981), pp. 71-77. The value δ [(cal / cm ³ ) ^1/2 ] at 25 ° C. calculated by the Fedors equation described in 1 (cal / cm ³ ) ^1/2 = 2.05 (MJ / m ³ ) ¹ Therefore, an SP value of 10 (cal / cm ³ ) ^1/2 or less means 20.5 (MJ ^/ m ³ ) ^1/2 or less.
Fedors formula:
SP value (δ) = (E _v / v) ^1/2 = (ΣΔe _i / ΣΔv _i ) ^1/2
E _v : Evaporation energy v: Molar volume Δe _i : Evaporation energy of atoms or atomic groups of each component Δv _i : Molar volume of each atom or atomic group
For the evaporation energy and molar volume of each atom or group used in the calculation of the above equation, refer to F. Fedors, Polym. Eng. Sci., 14, 147 (1974).

In the rubber composition according to the present embodiment, the content of the polymer particles made of the (meth) acrylate-based polymer is 1 to 100 parts by mass, preferably 1 to 100 parts by mass with respect to 100 parts by mass of the rubber component made of diene-based rubber. It is 2 to 50 parts by mass, more preferably 3 to 30 parts by mass.

In the rubber composition according to the present embodiment, in addition to the polymer particles made of the (meth) acrylate-based polymer, a reinforcing filler, a silane coupling agent, an oil, zinc oxide, stearic acid, an antiaging agent, and a wax are included. , Vulcanization agents, vulcanization accelerators, and various other additives generally used in rubber compositions can be blended.

As the reinforcing filler, for example, silica such as wet silica (hydrous silicic acid) or carbon black is used. Preferably, silica alone or a combination of silica and carbon black is preferable in order to improve the balance between rolling resistance performance and wet grip performance. The content of the reinforcing filler is not particularly limited, and may be, for example, 20 to 150 parts by mass or 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The content of silica is also not particularly limited, and may be, for example, 20 to 150 parts by mass or 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

When silica is blended, it is preferable to use a silane coupling agent in combination, in which case the content of the silane coupling agent is preferably 2 to 20% by mass, more preferably 4 to 15% by mass of the silica mass. %.

Sulfur is preferably used as the vulcanizing agent. The content of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. Examples of the vulcanization accelerator include various vulcanization accelerators such as sulfenamide-based, thiuram-based, thiazole-based, and guanidine-based, and any one of them may be used alone or in combination of two or more. be able to. The content of the vulcanization accelerator is not particularly limited, but is preferably 0.1 to 7 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component. ..

The rubber composition according to the present embodiment can be produced by kneading according to a conventional method using a commonly used mixer such as a Banbury mixer, a kneader, or a roll. That is, for example, in the first mixing step, the polymer particles are added and mixed with other additives other than the vulcanizing agent and the vulcanization accelerator, and then the final mixing is performed with the obtained mixture. A rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator at the stage.

The rubber composition for tires thus obtained is applied to various parts of tires such as tread parts and sidewall parts of pneumatic tires of various uses and sizes such as passenger car tires and large tires for trucks and buses. be able to. That is, the rubber composition is molded into a predetermined shape by, for example, extrusion processing according to a conventional method, and after producing a green tire by combining with other parts, the green tire is vulcanized and molded, for example, at 140 to 180 ° C. Thereby, a pneumatic tire can be manufactured. Among these, it is particularly preferable to use it as a compound for tire tread.

Hereinafter, examples of the present invention will be shown, but the present invention is not limited to these examples.

[Measuring method of average particle size]
The average particle size of the polymer particles is the particle size (50% diameter: D50) at an integrated value of 50% in the particle size distribution measured by the dynamic light scattering method (DLS), and is dynamic light scattering manufactured by Otsuka Electronics Co., Ltd. It was measured by a photon correlation method (JIS Z8826 compliant) using a photometric meter "DLS-8000" (angle between incident light and detector 90 °), and was obtained by the Cumulant method from the obtained autocorrelation function.

[Measurement method of Tg]
The Tg of the polymer particles was measured at a heating rate of 20 ° C./min by a differential scanning calorimetry (DSC) method in accordance with JIS K7121 (measurement temperature range: −150 ° C. to 150 ° C.).

<Synthesis Example 1>
15.0 g of 2,4,6-trimethylheptyl methacrylate (isodecyl methacrylate), 0.394 g of ethylene glycol dimethacrylate, 1.91 g of sodium dodecyl sulfate, 120 g of water and 13.5 g of ethanol are mixed. The monomer was emulsified by stirring for 1 hour, 0.179 g of potassium persulfate was added, and then nitrogen bubbling was performed for 1 hour, and the solution was held at 70 ° C. for 8 hours to synthesize a polymer particle dispersion emulsion. did. Polymer particles A were obtained by coagulation by adding methanol to the obtained solution. The average particle size was 60 nm and Tg was −37 ° C.

<Synthesis example 2>
15.0 g of 2-ethylhexyl methacrylate, 0.450 g of ethylene glycol dimethacrylate, 2.18 g of sodium dodecyl sulfate, 120 g of water and 13.5 g of ethanol are mixed and stirred for 1 hour to emulsify the monomer. , 0.204 g of potassium persulfate was added, and polymer particles B were obtained by the same method as in Synthesis Example 1. The average particle size was 58 nm and the Tg was −10 ° C.

<Synthesis Example 3>
15.0 g of n-dodecyl methacrylate, 0.351 g of ethylene glycol dimethacrylate, 1.70 g of sodium dodecyl sulfate, 120 g of water and 13.5 g of ethanol are mixed and stirred for 1 hour to emulsify the monomer. , 0.159 g of potassium persulfate was added, and polymer particles C were obtained by the same method as in Synthesis Example 1. The average particle size was 62 nm and the Tg was −65 ° C.

<Processing example 1>
The polymer particles A obtained in Synthesis Example 1 are redispersed in a solvent by immersing them in a tetrahydrofuran (THF) solvent having an sp value of 9.1, and then redispersed by adding methanol. It was solidified to obtain polymer particles 1.

<Processing example 2>
Polymer particles 2 were obtained by redispersion and recoagulation according to Treatment Example 1 except that acetone having an sp value of 9.9 was used instead of tetrahydrofuran.

<Processing example 3>
Polymer particles 3 were obtained by redispersion and recoagulation according to Treatment Example 1 except that toluene having an sp value of 8.9 was used instead of tetrahydrofuran.

<Processing example 4>
Polymer particles 4 were obtained by redispersion and recoagulation according to Treatment Example 1 except that n-hexane having an sp value of 7.3 was used instead of tetrahydrofuran.

<Processing example 5>
Polymer particles 5 were obtained by redispersion and recoagulation according to Treatment Example 1 except that diethyl ether having an sp value of 7.4 was used instead of tetrahydrofuran.

<Processing example 6>
Polymer particles 6 were obtained by redispersion and recoagulation according to Treatment Example 1 except that isopropyl alcohol having an sp value of 11.5 was used instead of tetrahydrofuran.

<Processing example 7>
Polymer particles 7 were obtained by redispersion and recoagulation according to Treatment Example 1 except that ethanol having an sp value of 12.7 was used instead of tetrahydrofuran.

<Processing example 8>
The polymer particles 8 were obtained by redispersion and recoagulation according to Treatment Example 1 except that the polymer particles B were used instead of the polymer particles A.

<Processing example 9>
The polymer particles 9 were obtained by redispersion and recoagulation according to Treatment Example 1 except that the polymer particles C were used instead of the polymer particles A.

The redispersibility and recoagulability of the polymer particles 1 to 9 were evaluated, the amount of impurities was measured for the polymer particles A to C and the polymer particles 1 to 9, and the results are shown in Table 1. The evaluation method and the measurement method are as shown below. The average particle size and Tg of the polymer particles after the recoagulation treatment were not measured because it can be estimated that they are the same as those before the treatment.

-Redispersity: It was visually confirmed whether the polymer particles were redispersed in the solvent, and those that were well dispersed were marked with "○" and those that were not redispersed were marked with "x".

-Re-coagulation: It was visually confirmed whether the polymer was re-coagulated, and those that were re-coagulated were marked with "○" and those that were not re-coagulated were marked with "x".

-Amount of impurities ([Na ⁺ + K ⁺ ]): 5 ml of nitric acid was added to 0.1 g of the obtained polymer particles, decomposed by microwave, and diluted to 50 ml with distilled water to prepare a measurement solution. Inductively coupled plasma emission spectrometry (ICP-OES) was performed using "Optima 8300" manufactured by PerkinElmer Co., Ltd., and the sodium concentration and the potassium concentration were measured, and the total value was obtained.

Using a lab mixer, first, in the first mixing step, other compounding agents other than sulfur and vulcanization accelerator were added to the diene-based rubber component and kneaded according to the compounding (part by mass) shown in Table 2 below (). Discharge temperature = 160 ° C). Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product in the final mixing step and kneaded (discharge temperature = 90 ° C.) to prepare a rubber composition. The details of each component in Table 2 are as follows.

-Denatured SBR: "HPR350" manufactured by JSR Corporation
・ BR: "BR150B" manufactured by Ube Industries, Ltd.
・ Silica: "Nip Seal AQ" manufactured by Tosoh Silica Co., Ltd.
-Silane coupling agent: Bis (3-triethoxysilylpropyl) tetrasulfide, "Si69" manufactured by Evonik Japan Co., Ltd.
-Polymer particles A to C: Polymer particles obtained in the above synthesis examples 1 to 3, respectively-Polymer particles 1 to 9: Polymer particles obtained in the above treatment examples 1 to 9, respectively-Zinc oxide: Mitsui Metal Mining Co., Ltd. Made by "Zinc Oxide 1"
・ Anti-aging agent: "Nocrack 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
-Stearic acid: "Lunac S-20" manufactured by Kao Corporation
・ Sulfur: "Powdered sulfur 150 mesh for rubber" manufactured by Hosoi Chemical Industry Co., Ltd.
・ Vulcanization accelerator: "Noxeller CZ" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
-Secondary vulcanization accelerator: "Noxeller D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Each of the obtained rubber compositions was vulcanized at 160 ° C. for 20 minutes to prepare a test piece having a predetermined shape, and a dynamic viscoelasticity test was performed using the obtained test piece at 0 ° C. and 60 ° C. The tan δ was measured at.

Wet grip performance: Using the UBM Leospectometer E4000, the loss coefficient tan δ was measured under the conditions of frequency 10 Hz, static distortion 10%, dynamic distortion 2%, and temperature 0 ° C., and the value of Comparative Example 1 was set to 100. It is displayed by the index. The larger the index, the larger the tan δ, indicating that the wet grip performance is excellent.

-Fuel efficiency: The temperature was changed to 60 ° C., and tanδ was measured in the same manner as tanδ at 0 ° C., and the value of Comparative Example 1 was set to 100 and displayed as an index. The smaller the index, the less likely it is that heat will be generated, the smaller the rolling resistance of the tire, and the better the rolling resistance performance (that is, fuel efficiency).

The results are as shown in Table 2, and it can be seen that in Examples 1 to 5, fuel efficiency was improved while maintaining excellent wet grip performance as compared with Comparative Examples 2 to 8.

It can be seen that Comparative Examples 2, 7 and 8 containing the polymer particles A to C had insufficient effect of improving fuel efficiency or deteriorated fuel efficiency as compared with Comparative Example 1.

The rubber composition for tires of the present invention can be used for various rubber compositions for tires such as passenger cars, light trucks and buses.

Claims (3)

Polymer particles having an alkyl (meth) acrylate unit represented by the formula (1) as a constituent unit with respect to 100 parts by mass of a rubber component made of a diene rubber, and the total amount of sodium concentration and potassium concentration is 2000 ppm or less. Contains 1 to 100 parts by mass ,
A rubber composition for a tire in which sodium or potassium in the polymer particles is present as a fatty acid salt or a persulfate .

In the formula, R ¹ is a hydrogen atom or a methyl group, R ¹ in the same molecule may be the same or different, R ² is an alkyl group having 4 to 18 carbon atoms, and R ² in the same molecule is. It may be the same or different. The rubber composition for a tire according to claim 1, wherein the polymer particles have a glass transition temperature of −70 to 0 ° C. A pneumatic tire produced by using the rubber composition for a tire according to claim 1 or 2 .